Precision getter alignment for cathode ray tubes

ABSTRACT

In a cathode ray tube a getter assembly, supported from the electron gun assembly, is precisely positioned within the tube by use of a locating channel formed in the side wall of a metallic, generally cup-shaped end member of the electron gun assembly. This allows consistent alignment with a coil energized by radio frequency current and situated outside the tube, but adjacent thereto, to heat and evaporate getter material within the tube. The channel may be formed by inwardly piercing two parallel slots in the end member and employing the introverted metal to restrain the getter support member.

United States Patent Krackhardt et al.

PRECISION GETTER ALIGNMENT FOR CATHODE RAY TUBES Sept. 16, 1975 3,689,791 9/1972 McQueen et a1. 313/412 3,711,734 1 1973 Yamazaki et 8.1..... 313/178 x 3,728,569 4/1973 Gerritsen 313/412 3,735,179 5/1973 Kaplan 313 402 Primary Examiner-Robert Segal [57] ABSTRACT In a cathode ray tube a getter assembly, supported from the electron gun assembly, is precisely positioned within the tube by use of a locating channel formed in the side wall of a metallic, generally cup-shaped end member of the electron gun assembly. This allows consistent alignment with a coil energized by radio frequency current and situated outside the tube, but adjacent thereto, to heat and evaporate getter material within the tube. The channel may be formed by inwardly piercing two parallel slots in the end member and employing the introverted metal to restrain the getter support member.

8 Claims, 9 Drawing Figures 32, 46 l u I 34 F 1 i g 20 PATENTEDSEP 1 6 I975 3. 906,282

RADIO FREQUENCY POWER SUPPLY PRECISION GETTER ALIGNMENT FOR CATHODE RAY TUBES INTRODUCTION This invention relates to adsorption of residual free gases within cathode ray tubes, and more particularly to apparatus for maximizing yield of evaporated getter material within such tubes.

In manufacturing cathode ray tubes, particularly television picture tubes, getter material is typically evaporated onto the inside surfaces of the walls of the tube. This is done in order that the material be provided with a large amount of surface area so as to adsorb residual free gases remaining in the tube after the tube has been evacuated to its low operating pressure, usually by a vacuum pump, and sealed.

The getter material is normally held in a container within the tube while the tube is being evacuated. After the tube has been evacuated, the getter material is heated to a sufficiently high temperature such that it evaporates, or is flashed, and condenses upon the relatively cool interior surfaces of the tube. The getter material, usually comprised of an alkaline earth metal such as barium, has the capability of adsorbing or reacting with large quantities of gas molecules, with its adsorption capability being substantially proportional to its surface area exposed to the interior of the tube. Throughout the lifetime of the tube, the getter material functions to remove any further gases that might be liberated from the tube components.

In flashing the getter, the container of getter material is typically heated by induction; that is, a radio frequency current is permitted to flow in a coil external to the tube, but situated close to the tube envelope in the region of the getter material container. The radio frequency electromagnetic field thus established by the coil extends through the envelope of the tube, which is normally comprised of glass that exhibits a permeability close to that of empty space, and creates eddy currents within the getter material and its container. The energy of these eddy currents is dissipated in heat, producing a sufficient temperature rise to flash the getter material. The flashed getter material deposits itself mainly on the exposed portions of the aperture mask and the interior surface of the glass envelope.

In production of television picture tubes, a precise amount of getter material is measured into each getter material container, so as to achieve a desired distribution of getter material within the tube after flashing. For greater economy in manufacture, substantially the entire amount of getter material should be flashed so as to avoid waste of getter material remaining in its container after flashing. Thus it is desirable to measure the amount of getter material added to the container so that the material to be flashed is sufficient to remove, essentially completely, the residual gases, but not so excessive as to condense on the vital components of the tube to the extent of impairing tube operation.

Two methods of obtaining proper placement of getters in picture tubes have been commonly known in the art. One method involves jigging the getter assembly for welding onto the generally cup-shaped end member of the electron gun assembly. However, this type of assembly requires fixture maintenance and results in relatively slowproduction rates. The second method involves keying the getter support member, by means of a slot, to magnetic isolating shields in the generally cupshaped end member. However, magnetic isolating shields are not normally employed in inline electron gun assemblies which are becoming prevalent in color television picture tubes. The present invention, therefore, is directed to novel apparatus for assuring flashing of uniform quantities of getter material by heating the getter material uniformly from one cathode ray tube to the next on a production line, and has applicability to a wide variety of cathode ray tube types.

Accordingly, one object of the invention is to provide apparatus to assure flashing of a uniform quantity of getter material in each cathode ray tube on a production line.

Another object is to achieve high yields in flashing getter material in cathode ray tubes on a production line.

Another object of the invention is to provide a television picture tube wherein a quantity of getter material is positioned with a high degree of accuracy prior to flashing.

Briefly, in accordance with a preferred embodiment of the invention, a cathode ray tube comprises electron gun means for producing at least one beam of electrons, generally cup-shaped apparatus situated at the end of the electron gun means from which the electrons are emergent and including a side wall, and means located within the tube for gettering gases therein. Apparatus is provided within the tube for retaining the means for gettering gases in precise alignment on a radial axis of the tube and comprises a predetermined configuration of getter material, a channel formed longitudinally in the side wall of the generally cup-shaped apparatus, and a member supporting the predetermined configuration of getter material. The member is positioned within the channel and affixed to the generally cup-shaped apparatus so as to extend toward a predetermined location in the tube.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram illustrative of the process of flashing a getter in a cathode ray tube;

FIG. 2 is a partially broken-away and fragmentary view illustrating the invention as employed in a color television picture tube;

FIG. 3 is a view taken along lines 33 in FIG. 2;

FIG. 4 is a simplified view of a convergence cup in a color television picture tube electron gun assembly fabricated in accordance with the teachings of the invention;

FIG. 5A is a view taken along line 55 in FIG. 4, showing one embodiment of the structure of FIG. 4;

FIG. 5B is a view taken along line 5-5 in FIG. 4, showing an alternate embodiment of the structure of FIG. 4;

FIG. 6 is a simplified view of another convergence cup in a color television picture tube electron gun assembly fabricated in accordance with the teachings of the invention;

FIG. 7 is a view taken along line 7-7' in FIG. 6, and

FIG. 7A is a view of a modified portion of the apparatus shown in FIG. 7.

DESCRIPTION OF TYPICAL EMBODIMENTS In FIG. 1, a cathode ray tube 10 is illustrated schematically as having a phosphor screen 9 at one end and including an electron gun assembly 11 at the opposite end. A container 12 holding a predetermined quantity of getter material is supported by a member 13 affixed to assembly 11, and rests against the inner surface of the envelope of tube 10 on a support 19 attached to the container. A coil of wire 14 is situated at a predetermined stationary location outside of, and adjacent, the envelope of tube 10, and is energized with radio frequency current from a radio frequency power supply 15 when the getter is to be flashed.

To evaporate getter material from container 12, which conveniently may comprise a ring-shaped channel, coil 14 is aligned with the container such that a radio frequency field generated by the coil links with, and heats, container 12. To obtain high yields of evaporated getter material, precise axial alignment between coil 14 and container 12 is necessary; a 1/ 16th inch positional error between the coil and the container is detrimental to this high yield objective. Because coil 14 has a fixed position external to the glass envelope of picture tube 10, an electron gun assembly 11 is situated in a fixed position inside the glass envelope by wellknown methods commonly employed in assembling and processing color television picture tubes. Therefore, if container 12 is properly supported and attached to electron gun assembly 11, accurate alignment with coil 14 is obtained. Consequently, when coil 14 is energized with radio frequency current, the field produced by the coil will heat container 12 and the getter material therein in a uniform, predictable manner, resulting in evaporation of a precise amount of getter material within tube 10.

In order for container 12 to be in precise alignment with the longitudinal axis 16 of coil 14, it is necessary that container 12 be situated on the proper radial axis 18 of tube 10 at a predetermined distance from electron gun assembly 1 1. Radial axis 18 is normal to longitudinal axis 17 of tube 10 and, as described, infra, is at a predetermined angle with respect to the horizontal and vertical axes of the tube.

FIG. 2 illustrates the present invention as employed in a color television picture tube of the inline gun assembly type. Final electrodes 20, 21 and 22 of three electron guns, supported by metallic strap means 24 attached to glass support means or beads 25, are shown adjacent a metallic, generally cup-shaped electrode 23, termed a convergence assembly of convergence cup, which functions to provide convergence of the three electron beams produced by the electron guns; that is, the three electron beams are caused to converge at a predetermined point close to the cathode ray tube screen so as to assure registration of each electron beam upon the correct phosphor on the screen to produce the proper color. To assist in accomplishing convergence, magnetic fields are typically established through the convergence assembly in a manner wellknown in the art and described, for example, in Krackhardt et al. US. Pat. No. 5,534,208, issued Get. 13, 1970 and assigned to the instant assignee. Specifically, pole piece assemblies 46 and 47 furnish horizontal deflection of the outer beams in an inline electron gun assembly as described, infra.

Spring clips of snubber springs 26 are attached to convergence assembly 23, as by welding, and serve to hold the electron gun assembly in alignment with the neck of the cathode ray tube in which it is used, as well as to provide electrical connection of the electron gun assembly to an electrically conductive coating or paint carrying high voltage on the inside surface of the tube envelope. A getter assembly 27 typically comprises getter material 28 held within container 12. Getter assembly 27 is supported by one end of a strip or antenna 31. The opposite end of antenna 31 is attached to convergence assembly 23. A typical getter assembly and support therefor are described in greater detail in C. R. Kalbfus US. Pat. No. 3,547,255, issued Dec. 15, 1970 and assigned to the instant assignee.

To assure accurate positioning of getter assembly 27 in a cathode ray tube, two parallel portions 32 and 33 of the generally curved side wall of convergence assembly 23 are introverted or bent inwardly to form a channel into which antenna 31 is fitted. This may be seen through the cutaway section of convergence assembly 23 in FIG. 2. The length of antenna 31, which is cut to a precise, predetermined length, is fitted between wall segments 32 and 33 such that its end abuts the base 30 of the convergence assembly, and is affixed in position as by welds 34 which join antenna 31 to the web portion (not shown) of the channel defined by segments 32 and 33. This ensures that antenna 31 will extend toward the proper location in the tube for correct placement of getter assembly 27 at a predetermined distance from convergence cup 23 measured longitudinally along the inside surface of the tube. Additionally, segments 32 and 33 are not only parallel to each other, but are also parallel to the longitudinal axis of the tube so as to retain antenna 31 in a plane containing the longitudinal axis of the tube, which plane is at a precise angle with respect to a plane containing the longitudinal axis of each of the electron guns. This is evident in FIG. 3, which is a simplified view of convergence assembly 23 taken along line 3-3' in FIG. 2.

In FIG. 3, apertures 43, 44 and 45 in the base 30 of convergence assembly 23 are shown along a plane 36 which, as viewed edgewise, contains the longitudinal axis of each electron gun and represents the horizontal axis of the cathode ray tube in which the invention is utilized. Location of the center of antenna strip 31 is determined by another plane 38 that as viewed edgewise, contains the longitudinal axis of the center electron gun (which is also the longitudinal axis of the tube) and is offset from plane 36 by a preciselydetermined angle 0. The intersection of plane 38 with a plane normal to the longitudinal axis of the tube and spaced at the proper distance from convergence cup 23 defines the proper radial axis for antenna strip 31.

Convergence assembly 23 includes a first set of pole pieces comprised of metal plates 46 and 47, and a second set of pole pieces comprised of metal plates 48 and 49, each plate being attached to the generally curved pieces in the manner described in the aforementioned Krackhardt et al. US. Pat. No. 3,534,208 applies a horizontal deflecting field to the two outer electron beams.

FIG. 4 is a simplified view of convergence cup 23 of FIGS. 2 and 3, showing a pair of open slots 50 and 51 therein, running parallel to longitudinal axis 17 of the cathode ray tube in which the convergence assembly is to be employed and defining a segment 52 therebetween. These slots are produced when portions of the generally curved side wall of convergence cup 23 are introverted in either parallel planes, or radial planes. Thus, FIG. 5A is a view along 5-5 of FIG. 4 when the inwardly-bent segments 53 and 54 of the side wall of convergence cup 23 are formed in parallel planes. Segments 53 and 54, together with web portion 52, form a channel having parallel walls between which a getter assembly antenna may be fitted and supported while being welded to web portion 52. Similarly, FIG. 5B is a view along line 55 of FIG. 4 when inwardly-bent segments 53 and 54 are formed in radial planes. Segments 53 and 54, together with web portion 52, form a channel having inwardly-slanted walls between which a getter assembly antenna may be fitted. The inwardlyslanted walls in the embodiment of FIG. 5B are especially advantageous in retaining the getter assembly antenna in place while it is being welded to web portion 52 of the channel.

FIG. 6 is another simplified view of convergence cup 23 of FIGS. 2 and 3, showing a pair of open slots 60 and 61 therein, running parallel to longitudinal axis 17 of the cathode ray tube in which the convergence assembly is to be employed, and defining a segment 62 therebetween. Slots 60 and 61 are more widely separated from each other than slots 50 and 51 in the embodiment shown in FIG. 4. This is because the portions of the side wall of convergence cup 23 that are bent inwardly in this embodiment are formed integrally with segment 62. Formation of the structure shown in FIG. 7, which represents a view along line 7-7' of FIG. 6, results. In the embodiment of FIG. 7, segments 63 and 64, together with web portion 62, form a channel having parallel walls between which a getter assembly antenna may be fitted and supported while being welded to web portion 62.

Although segments 63 and 64 of FIG. 7 are shown in parallel planes, it will be apparent to those skilled in the art that these segments could be introverted along radial planes, for example, in a manner similar to that illustrated in FIG. 5B. The channel resulting from such structure is shown in FIG. 7A, where like reference nu merals indicate like components.

The foregoing describes apparatus to assure flashing of a uniform quantity of getter material in each cathode ray tube on a production line. The invention permits high yields in flashing the getter material on a production basis by insuring that it is positioned with a high degree of accuracy within each cathode ray tube prior to flashing.

While only certain preferred features of the invention have been shown by way of illustration, may modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

We claim:

1. In a cathode ray tube including electron gun means for producing at least one beam of electrons, generally cup-shaped apparatus situated at the end of said electron gun means from which said electrons are emergent, said generally cup-shaped apparatus including a side wall, and means located within said tube for gettering gases therein, apparatus for retaining said means for gettering gases in precise alignment on a radial axis of said tube comprising:

a predetermined configuration of getter material;

a channel formed longitudinally in the side wall of said generally cup-shaped apparatus, said channel including sides formed by introverted segments of said side wall and a web portion formed by the portion of said side wall situated between said segments, and a member supporting said configuration of getter material, said member being positioned within said channel and afiixed to said generally cup-shaped apparatus so as to extend toward a predetermined location in said tube.

2. The combination of claim 1 wherein said member is welded to said web portion.

3. The combination of claim 1 wherein said member is of predetermined length, one end of said member abutting the base of said generally cup-shaped apparatus.

4. The combination of claim 3 wherein said member is welded to said web portion.

5. In a cathode ray tube including electron gun means for producing at least one beam of electrons, generally cup-shaped apparatus situated at the end of said electron gun means from which said electrons are emergent, said generally cup-shaped apparatus including a side wall, and means located within said tube for gettering means therein, apparatus for retaining said means for gettering gases in precise alignment on a radial axis of said tube comprising:

a predetermined configuration of getter material;

a channel formed longitudinally in the side wall of said generally cup-shaped apparatus, said channel including sides formed by introverted segments of a web portion formed by the portion of said side wall situated between two, substantially parallel slots in said side wall; and

a member supporting said configuration of getter material, said member being positioned within said channel and afiixed to said generally cup-shaped apparatus so as to extend toward a predetermined location in said tube.

6. The combination of claim 5 wherein said member is welded to said web portion.

7. The combination of claim 5 wherein said member is of predetermined length, one end of said member abutting the base of said generally cup-shaped apparatus.

8. The combination of claim 7 wherein said member is welded to said web portion. 

1. In a cathode ray tube including electron gun means for producing at least one beam of electrons, generally cup-shaped apparatus situated at the end of said electron gun means from which said electrons are emergent, said generally cup-shaped apparatus including a side wall, and means located within said tube for gettering gases therein, apparatus for retaining said means for gettering gases in precise alignment on a radial axis of said tube comprising: a predetermined configuration of getter material; a channel formed longitudinally in the side wall of said generally cup-shaped apparatus, said channel including sides formed by introverted segments of said side wall and a web portion formed by the portion of said side wall situated between said segments, and a member supporting said configuration of getter material, said member being positioned within said channel and affixed to said generally cup-shaped apparatus so as to extend toward a predetermined location in said tube.
 2. The combination of claim 1 wherein said member is welded to said web portion.
 3. The combination of claim 1 wherein said member is of predetermined length, one end of said member abutting the base of said generally cup-shaped apparatus.
 4. The combination of claim 3 wherein said member is welded to said web portion.
 5. In a cathode ray tube including electron gun means for producing at least one beam of electrons, generally cup-shaped apparatus situated at the end of said electron gun means from which said electrons are emergent, said generally cup-shaped apparatus including a side wall, and means located within said tube for gettering means therein, apparatus for retaining said means for gettering gases in precise alignment on a radial axis of said tube comprising: a predetermined configuration of getter material; a channel formed longitudinally in the side wall of said generally cup-shaped apparatus, said channel including sides formed by introverted segments of a web portion formed by the portion of said side wall situated between two, substantially parallel slots in said side wall; and a member supporting said configuration of getter material, said member being positioned within said channel and affixed to said generally cup-shaped apparatus so as to extend toward a predetermined location in said tube.
 6. The combination of claim 5 wherein said member is welded to said web portion.
 7. The combination of claim 5 wherein said member is of predetermined length, one end of said member abutting the base of said generally cup-shaped apparatus.
 8. The combination of claim 7 wherein said member is welded to said web portion. 